This invention relates to safety valves for use in fuel dispensing systems and, more specifically, to such fuel dispensing systems including vapor recovery systems.
Fuel dispensing systems at, for example, vehicle service stations, have long been provided with a variety of safety devices to preclude minor accidents occurring in the vicinity of the fuel pumps from resulting in large fuel spills which could lead to large fires and/or explosions. In the usual case, a safety valve is located in the fuel dispensing line, at the pump and is secured to the pump island. The safety valve includes a normally closed valve which is latched in an open condition to allow fuel to flow. Typically, the latch includes a fusible link so that an elevated temperature in the vicinity of the safety valve as, for example, caused by a small fire, would result in the melting of the link and the closing of the valve.
Such valves also typically include an intentionally weakened portion spanned by the link maintaining the valve open such that if sufficient force is applied to the safety valve body, as, for example, by a collision of a vehicle with the pump, the valve body will rupture so that the latch link is displaced, allowing the valve to close.
Recently, increasing environmental concerns regarding air pollution by hydrocarbons has resulted in the large scale introduction of vapor recovery systems in such fuel dispensers. Typically, the fuel dispensing nozzle is provided with a vapor collector which collects vapors driven from a fuel tank during the filling process and/or liquid fuel driven into the collector as by splashing or overfilling of the tank. Such vapors and liquid fuel are conveyed, usually by a vacuum, to vapor recovery systems which condense the vapor and return the same in a liquid form along with any liquid fuel collected to the fuel storage tank.
Because the vapor recovery lines, when in operation, are conducting a flammable vapor and/or liquid, it is highly desirable to provide means for precluding vapor and/or liquid in the vapor recovery system from spilling or otherwise exiting the system in the case of an accident in the vicintiy of the pump to minimize or eliminate fire and explosion danger.